Coronaviruses are now known to be significantly involved in respiratory infections of man. Details of this involvement are not known. The total number and interrelationships of the coronaviruses are also not defined at present. It is therefore proposed to determine optimal cell culture or other techniques for isolation and propagation of these viruses. The studies will initially be performed with known prototype viruses. Thereafter, throat specimens collected during the course of the 6 year Tecumseh Study of Respiratory Infection will be tested for the presence of coronaviruses. Isolates will be identified and related to known coronaviruses through use of hyperimmune animal sera. The human sera collected during the course of the Tecumseh Study will be used to help in defining the interrelationships of the viruses, and also to determine the extent of infection caused by them. Tests to be employed will be complement fixation, hemagglutination-inhibition and neutralization. These results will be compared with illness data so that the role of the coronaviruses in the etiology of respiratory disease can be determined.